Hello Forum Members,
So I have started the project, and almost finished it. As I have a little time, I thought I'll share the process with some pics I did.
First, I managed to put together the main box, and cut some dampening, which came out fast, after testing if they fit fine...

Then drilled out the handle holes, the L-pad hole, speakon input, and the place of the speakers

Then tested the speakers, if they fit in nicely

Then did the crossovers, and found a good place to fix, installed the L-Pad, and had a first test, if the speakers are working right... they did!

So, the next step is glueing the front, glue the carpet, and get some speaker grill...

Sorry for the unorthodox picture orientation, if someone can tell me how to fix them here... the source's orientation is good.